COLLECTIONSChapter 5 · Collections

Dictionary methods

.get(key, default) reads a value without crashing when the key is missing. .keys(), .values() and .items() let you loop over a dictionary, and .items() gives you each key and value together. .update(other) merges another dict in, and .pop(key) removes an entry and returns its value.

Worked example

How it reads

.get("color", "unknown") falls back to the default instead of raising KeyError
.update adds new keys and overwrites existing ones
for key, value in star.items() unpacks each pair

Common mistakes

d["missing"] raises KeyError. Use d.get("missing") when a key might not be there.
Adding or removing keys while looping over the same dict raises RuntimeError. Loop over list(d.items()) instead.

Cloud tip: Counting things? counts[word] = counts.get(word, 0) + 1 is the classic one-liner.